It has taken nearly 50 years and cost £2.6bn. Now, at last, the Higgs
boson particle has been found - and a new chapter in our understanding
of the universe can begin
It was a breakthrough that took almost half a century of deep thought,
more than 30 years of painstaking experimentation and a massive £2.6bn
machine. Yesterday, scientists said they believed they had found the
subatomic particle that confirms our understanding of how the universe
works.
Discovering the so-called "Higgs boson" particle would be one of the
greatest achievements in science, rivalling the discovery of the
structure of DNA in 1953 and the Apollo Moon landings of the 1960s and
1970s. It can explain why some particles have mass, but why others, such
as photons of light, do not.
Although the discovery is consistent with such a particle – first
postulated half a century ago by the retired British physicist Peter
Higgs – scientists at the European Organisation for Nuclear Research
(Cern) in Geneva stopped short of saying this was definitely what they
had found.
Yet such is the degree of exactitude to which they work, they were still
able to calculate that the new particle is very near to the
"five-sigma" level of significance – meaning that there is less than a
one in a million chance that their results are a statistical fluke.
A Higgs boson particle is essential to the so-called Standard Model of
physics – the generally accepted theory about how the Universe works.
Finding it would effectively confirm the Standard Model, explaining the
results of countless physics experiments and why other particles behave
the way they do. Knowing definitively that it exists would show science
is heading in the right direction and will allow researchers to
concentrate their efforts accordingly – opening the door to new
discoveries.
One Nobel prize-winning physicist famously called it the "God particle"
because of its central role in theoretical physics – although Professor
Higgs and his colleagues at Cern have come to despise the term and its
religious undertones.
Higgs, 83 and long retired from the University of Edinburgh, was in the
audience yesterday in Geneva to hear the results of the two largest
experiments attached to the Large Hadron Collider, the circular
underground machine that smashes sub-atomic particles together at
enormous energy levels.
Both sets of experiments had neatly and independently confirmed the
existence of a new sub-atomic particle with a mass of about 125.5 GeV
(gigaelectron volts), which is about 133 times heavier than the protons
at the heart of every atom.
Professor Higgs, one of several retired scientists invited to listen in
person, wiped away tears as the data were revealed by Cern researchers.
He said he had asked his family back home in Edinburgh's Morningside to
put a bottle of champagne in the fridge.
Although the data just falls short of absolute confirmation, the
scientists were in little doubt that what they had found was a
sub-atomic entity fitting its description, as predicted by the Standard
Model of physics, a theoretical framework bringing together the
disparate forces of nature.
"As a layman, I would say that I think we have it. Do you agree?" said
Rolf Dieter Heuer, director general of Cern, at the end of the
presentations. The rapturous applause that met his hypothetical question
said it all.
"We have a discovery. We have observed a new particle consistent with a
Higgs boson? but which one, it remains open," he added. Further work
will be necessary to elucidate the precise characteristics of the new
sub-atomic particle – and whether it is indeed one of perhaps several
types of Higgs boson.
Theoretical physicists have long postulated that Higgs particles
permeate the Universe, creating an invisible energy field that causes
other particles of matter to have mass, allowing matter to coalesce into
larger objects such as molecules, stars and planets.
Joe Incandela, of Cerns's CMS experiment, explained the technical
details that led his team to the conclusion that the Higgs may have been
sighted. "We are seeing something and it is relatively significant? we
have a new boson," he said with the understatement of a scientist
working to confidence levels of greater than 99.9999 per cent. Cern's
Fabiola Gianotti echoed the conclusions of her colleagues working on the
CMS, saying that the data show a clear blip around the 125.5 GeV range
consistent with the Standard Model prediction of what the Higgs should
look like.
"It would be very nice for the Standard Model for the Higgs to be at
that mass. We all have to be proud of these results. They open a door to
a very bright future," she concluded at the end of her presentation.
Although the Higgs particle, more correctly termed the "scalar boson",
was first postulated in the early 1960s by a number of theoretical
physicists working independently, it was the powerful Large Hadron
Collider that enabled science to prove whether or not it does indeed
exist. The machine lies in a circular tunnel some 27km in circumference,
straddling the Franco-Swiss border just outside Geneva. Here, massive
magnets accelerate two opposing beams of protons to 99.9999991 per cent
of the speed of light in the hope of crashing them together in such a
way that a Higgs particle would momentarily pop out in view of the
detectors.
Once in a lifetime: Reaction from the world of science
Professor Brian Cox Broadcaster and particle physicist:
"It is the biggest scientific discovery of my lifetime and without doubt
one of the biggest scientific discoveries of all time. This day will go
down as one of the great days in the history of science."
Professor Sir Paul Nurse President of the Royal Society:
"The project at Cern is a testament to what can be achieved in science
when countries come together and pool resources and brains. Today moves
us a step closer to a fuller understanding of the very stuff of which
the universe is made."
Right Reverend Dr Lee Rayfield Scientist and Bishop of Swindon:
"This discovery provides crucial support that the prevailing scientific
theory for the nature of the universe is correct. That said – and
despite its nickname – the Higgs boson still leaves plenty of unanswered
questions that science alone can never address."
Professor Peter Higgs
Physicist who first suggested its existence said: "I am astounded at the
amazing speed with which these results have emerged. I never expected
this to happen in my lifetime."
Q&A: Why this particle matters
Q. What exactly is the "Higgs boson"?
A. A boson is a type of subatomic particle that imparts a force. The
Higgs boson was postulated in the early 1960s by Professor Peter Higgs
of Edinburgh University who suggested that its existence could explain
why matter, from atoms to planets, have mass rather than float around
the Universe without any mass, like photons of light.
Q How is the Higgs boson related to the Big Bang?
A About 13.7bn years ago the Big Bang gave birth to the universe and
caused an outburst of massless particles and radiation energy.
Scientists think that fractions of a second later, part of the radiation energy congealed into the Higgs field.
When the universe began to cool, particles acquired mass from the Higgs
field, slowed down and began to bunch up to form composite particles
and, eventually, atoms.
Conditions present a billionth of a second after the Big Bang are
|recreated in the Large Hadron |Collider particle accelerator near
Geneva.
Q How do you find a Higgs boson?
A Protons are spun at almost the speed of light in opposite directions
and smashed together. The enormous energy released is converted into new
particles.
Like other heavy particles, the Higgs decays into lighter particles,
which then decay into even lighter ones. The process can follow a
certain number of paths. Physicists compare the decay paths to predicted
decay paths. When a match is found, it suggests the observed particle
is the one being searched for.
Q. Why has it taken so long to find it?
A. Suggesting something in theory is one thing, but proving its
existence can be quite tricky. It seems that Higgs particles, if they do
indeed exist, only exist for a fraction of a second. Theory suggests
that enough of them should become detectable if beams of protons are
collided together at high enough energies. Until the Large Hadron
Collider was built a few years ago, previous colliders were not able to
reach these energy levels.
Q. So have scientists actually found the Higgs?
A. Not quite, or at least not to the confidence levels they would like
to achieve. They have definitely found a new subatomic particle with a
mass of about 130 protons and the preliminary results certainly fit in
with it being a Higgs boson. It may be the Higgs boson, or it may be one
of several – the theory suggests there may be more than one.
Q How did the Higgs boson get the nickname ‘the God particle’?
A Nobel laureate physicist Leon Lederman wrote a book in the early 1990s
about the search for the elusive Higgs boson. His publishers coined the
name as a marketable title for the book, but it's disliked by many
scientists.
Q. Why does such a discovery matter?
A. Physicists trying to understand the Universe have come up with a
theoretical framework that brings together the various forces of nature.
It is called the Standard Model. But the problem was that the model did
not explain why matter has mass, that is without invoking a Higgs
boson. So finding the Higgs is powerful support for the correctness of
the Standard Model. If the Higgs was not found, then the entire edifice
of modern theoretical physics would fall apart.
Q. Is this the end of particle physics?
A. It's just the end of the beginning. Confirming the existence of the
Higgs would only be the start of a new era of particle physics as
scientists focus on understanding how it works and look for unexpected
phenomena.
Q. Where do we go from here?
A. Further work will be necessary to confirm the new particle is indeed
the Higgs. The Large Hadron Collider meanwhile has many other projects
on the go, such as discovering "super symmetry", the idea that subatomic
particles have symmetrical twins.
Q. Did everyone think it would happen?
A. Not everyone. In 2000, Professor Stephen Hawking bet the University
of Michigan's Gordon Kane $100 that the Higgs would never be found.
Yesterday he admitted he would have to pay up.
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